The present invention generally relates to height adjustment for wheel assemblies, and more particularly to height adjustment in relation to structures utilizing caster wheels. The invention is particularly advantageous as applied to mobile equipment employing caster wheels such as lawnmowers.
Power equipment such as lawnmowers typically include a set of three or four wheels to support the equipment or a main structure thereof on the ground and to enable the equipment to be rolled along the ground. In the case of lawnmowers, and particularly walk-behind lawnmowers of either the self-propelled or manually pushed type, the main structure for which wheels are provided includes a mower deck to which a motor and cutting blades are mounted. The wheel set often includes one or two front wheels located at the front of the main structure and one or two rear wheels located at the rear of the main structure. Typically, the front and rear wheels are directly coupled to the mower deck, and often are rendered adjustable relative to the mower deck to provide a means by which the height of the mower deck relative to the ground can be adjusted. This height adjustment enables an operator of the lawnmower to cut grass or other vegetation to a desired height.
The means for height adjustment typically constitutes a lever and bracket mounted between each wheel and the mower deck. Adjustment of the lever to a selected position on the bracket, usually by rotating or pivoting the lever to engage a selected notch or aperture of the bracket, changes the angle of the lever relative to the mower deck. The lever is typically interfaced with the mower deck such that changing the angle of the lever changes the angle and spacing of the wheel relative to the mower deck. A lever and bracket can be provided for each wheel, necessitating the individual adjustment of each wheel to attain a desired, level height of the entire mower deck relative to the ground. In the case of a pair of front or rear wheels interconnected by a common axle, a similar means for adjusting the axle position relative to the mower deck can be implemented to adjust both front or rear wheels simultaneously.
In some lawnmowers, the front or rear wheels are provided in the form of caster wheels to improve maneuverability of the lawnmower. For three-wheel lawnmowers, one end (i.e., front or back) of the mower deck includes a pair of fixed-position wheels while the opposite end includes a single caster wheel. For four-wheel lawnmowers, a pair of caster wheels is usually mounted at the front of the mower deck and a pair of fixed-position wheels is mounted at the rear. For instance, a lawnmower equipped with one or two front-mounted caster wheels can be easily steered or turned left or right without having to first lift the front of the mower deck and front wheels off the ground, and without having to drag fixed-position wheels along the ground. As is appreciated by persons skilled in that art, a caster wheels, the caster wheel rotates about the horizontal axis that is generally axis of rotation and a horizontal rolling axis of rotation. Like fixed-position wheels, the caster wheel rotates about the horizontal axis that is generally parallel with the ground, enabling the lawnmower to be rolled forwardly or backwardly along the ground. Unlike fixed-position wheels, however, the caster wheel additionally rotates about the vertical axis, i.e., an axis perpendicular or substantially perpendicular to the ground that allows the caster wheel to be steered or swiveled, thereby enabling the rolling direction of the lawnmower to be changed to the left or to the right.
As is appreciated by persons skilled in the art, in order for a caster wheel-equipped lawnmower to be steered or turned properly, the verticality of the swivel axis of each caster wheel must be maintained. This limitation poses challenges to successfully rendering a caster wheel adjustable relative to mower deck height or, equivalently, rendering a mower deck adjustable relative to caster wheel height. For instance, a conventional lever that changes the angle between a wheel and a deck is unsuitable for use with a caster wheel, since such a lever would cause the swivel axis to deviate from the vertical and impair or even defeat the ability of the caster wheel or wheels to render the lawnmower steerable.
Accordingly, the adjustment means for a caster wheel is preferably designed to adjust the height of the horizontal rolling axis of the caster wheel, without altering the vertical orientation of its swivel axis. In the past, height adjustment for caster wheels has been addressed in a number of ways that have required undue complexity in terms of mechanical design, the use of tools, and/or an excessive expenditure of time. The difficulty presented in providing height-adjustable caster wheels is demonstrated by systems disclosed in the prior art. For example, in one known height-adjustment system, each caster wheel must be locked to prevent rotation and then adjusted individually through a traditional lever and bracket arrangement. In another known system, each wheel must be unbolted from the mower deck and then rebolted into new holes of the mower deck.
In another example, U.S. Pat. No. 4,942,726 to Bowditch discloses a lawnmower with two front-mounted, height-adjustable caster wheels. A pivotable lever is mounted on one side of the adjacent to the lever is a vertical plate that is provided with a series of notches. A pin extending transversely from the lever engages one of the notches to fix the lever in position and thus fix the height of the caster wheels relative to the mower deck. To adjust the height of the caster wheels relative to the mower deck, the lever is pivoted so as to move its pin into engagement with one of the notches of the vertical plate. The arrangement of the lever interfaced with the notched vertical plate is similar to conventional means for adjusting the height of fixed-position wheels, and is characterized by similar disadvantages. For lawnmowers of typical size and weight, the operator must use one hand to lift the mower deck to support its weight while using the other hand to operate the lever. Because the lever and associated vertical bracket are located at one side of the mower deck and operate to adjust both caster wheels simultaneously, the weight of the mower deck must be balanced while forcefully moving the lever from one notch of the bracket to another notch. Moreover, the protruding, exposed structure of the lever renders the lever susceptible to being jarred or knocked out of engagement with the desired notch and into re-engagement with a new notch, with the result that the mower deck is unintentionally adjusted to an undesired height during operation and out of agreement with the height relative to the other wheels. This problem has conventionally been addressed by constructing the lever from a stiff spring material that requires additional effort to be adjusted from one notch to another notch, further necessitating the use of both hands or otherwise increasing the effort required for effecting height adjustment of the caster wheels.
In U.S. Pat. No. 5,065,568 to Braun et al., a lawnmower with two front-mounted, height-adjustable caster wheels is disclosed in which a single crank handle mechanism mounted centrally at the front of the mower deck operates to adjust the height of the entire mower deck relative to both the caster wheels and the rear fixed-position wheels. The interface between the caster wheels, the crank handle mechanism, and the mower deck consists of an elaborate assembly including a transverse bar, hook brackets, push arms, a vertical rear plate, a tie rod, a central arm, a central linkage assembly, and a bell crank. To adjust the height of the caster wheels relative to the mower deck, the crank handle mechanism is turned by the operator, causing a number of interactions among the various afore-mentioned components and resulting in the raising or lowering of the mower deck. It can thus be seen that this height adjustment system adds undue complexity, weight, and cost to lawnmowers.
A much simpler approach to height adjustment of caster wheels for lawnmowers is disclosed in U.S. Pat. No. 5,960,615 to Meetze, in which an L-shaped bracket serves as a frame for supporting a pair of front-mounted caster wheels. Left and right vertically arranged sets of bolt holes are formed in the left and right sides of a vertical section of the L-shaped bracket. Corresponding left and right vertically arranged sets of receiving holes are formed in a front skirt section of the mower deck of the lawnmower. The L-shaped bracket is fixed to the mower deck by inserting a bolt through one of the left bolt holes of the L-shaped bracket and through one of the left receiving holes of the mower deck in alignment with the left bolt hole, and then threading the left bolt through a nut. This procedure is repeated for a bolt inserted through one of the right bolt holes and right receiving holes. To adjust the height of the caster wheels relative to the mower deck, the operator must remove the bolts to detach the L-shaped bracket from the mower deck, align a different pair of left and right bolt holes with a corresponding pair of receiving holes, and then secure the connection by re-inserting the bolts through the selected holes and re-threading the bolts into their respective nuts. This height adjustment system is disadvantageous in that it requires the use of a tool to effect the height adjustment.
In view of the foregoing examples of prior art, an ongoing need remains for providing an apparatus for adjusting the height of wheels, such as caster wheels, relative to a lawnmower or other structure in an efficient manner and with minimal effort, and without the use of tools or a complex system of components.
According to one embodiment, an apparatus for adjusting the height of a wheel, such as a caster wheel, in relation to a structure comprises a caster wheel rotatable about a vertical axis, a frame member, a hollow guide member, and a lever. The frame member is attached to the caster wheel for connecting the caster wheel to a structure. The frame member comprises an angled section disposed along an adjustment direction oriented at an angle relative to the vertical axis. The angled section comprises one or more recesses along the adjustment direction. The hollow guide member is adapted for attachment to the structure. The guide member is disposed around the angled section and has an interior oriented along the adjustment direction. The angled section is movable through the guide member along the adjustment direction. The lever comprises a locking element for engaging a selected one of the recesses to enable fixation of the angled section at a desired position relative to the guide member.
In one aspect of this embodiment, the angled section comprises first and second stop members axially spaced along the adjustment direction for constraining movement of the angled section through the guide member. The first and second stop members of the angled section can be provided by respective first and second slot ends of a slot formed in the angled section. A transverse element transversely extends through the slot, and is attached to the structure. The lever is pivotably connected to the transverse element. Accordingly, the movement of the angled section through the guide member is limited by the transverse element alternately contacting the first and second slot ends. In another aspect of this embodiment, a groove is formed in the angled section instead of a slot. The transverse element rides along the groove between first and second ends thereof, thereby limiting the movement of the angled section through the guide member. In yet another aspect of this embodiment, the first and second stop members of the angled section comprise first and second stop surfaces protruding from the angled section. Movement of the angled section through the guide member is limited by opposing ends of the guide member contacting the first and second stop surfaces.
According to another embodiment, an apparatus for adjusting the height of a wheel, such as a caster wheel, in relation to a structure comprises a caster wheel rotatable about a vertical axis, a frame member, a hollow guide member, an elongate element, and a lever. The frame member is attached to the caster wheel for connecting the caster wheel to a structure. The frame member comprises an angled section disposed along an adjustment direction oriented at an angle relative to the vertical axis. The angled section comprises a slot disposed along the adjustment direction, and a plurality of spaced recesses serially arranged along the adjustment direction. The hollow guide member is adapted for attachment to the structure. The guide member is disposed around the angled section and has an interior oriented along the adjustment direction. The angled section is movable through the guide member along the adjustment direction. The elongate element transversely extends through the slot, and is alternately contactable with first and second opposing slot ends of the slot. The first and second slot ends limit movement of the angled section relative to the guide member. The lever is pivotably connected to the elongate element and comprises a locking element for engaging a selected one of the recesses to enable fixation of the angled section at a desired position relative to the guide member.
According to yet another embodiment, an apparatus for adjusting the height of a wheel, such as a caster wheel, in relation to a structure comprises first and second caster wheels rotatable about respective parallel vertical axes, first and second frame members, a transverse frame member interconnecting the first and second frame members, first and second hollow guide members, first and second transverse elements, and a lever. The first frame member is attached to the first caster wheel for connecting the first caster wheel to a structure. The first frame member comprises a first angled section disposed along an adjustment direction oriented at an angle relative to the vertical axes. The first angled section comprises a pair of first stop members axially spaced along the adjustment direction, and a plurality of first recesses serially arranged along the adjustment direction. The second frame member is attached to the second caster wheel for connecting the second caster wheel to the structure. The second frame member comprises a second angled section disposed along the adjustment direction. The second angled section comprises a pair of second stop members axially spaced along the adjustment direction, and a plurality of second recesses serially arranged along the adjustment direction. The first and second hollow guide members are adapted for attachment to the structure. Each guide member is disposed around a respective angled section, and has an interior oriented along the adjustment direction. Each angled section is movable through a respective guide member along the adjustment direction. Movement of the angled sections is constrained between the respective pairs of first and second stop members. The first and second transverse elements are adapted for attachment to the structure. The lever is pivotably connected to and extends between the first and second transverse elements. The lever comprises first and second locking elements for respectively engaging a selected first recess and second recess to enable fixation of the first and second angled section at a desired height relative to the first and second guide members.
According to still another embodiment, a mobile apparatus is movable along a ground surface and is adapted for height adjustment relative to the ground surface. The apparatus comprises a set of wheels, a structure supported by the set of wheels, a frame member, a hollow guide member attached to the structure, a transverse element attached to the structure, and a handle. At least one of the wheels is a caster wheel rotatable about a vertical axis. The frame member interconnects the caster wheel and the structure. The frame member comprises an angled section disposed along an adjustment direction oriented at an angle relative to the vertical axis. The angled section comprises first and second stop members axially spaced along the adjustment direction, and a plurality of spaced recesses serially arranged along the adjustment direction. The hollow guide member is disposed around the angled section and has an interior oriented along the adjustment direction. The angled section is movable through the guide member along the adjustment direction. Movement of the angled section is constrained between the first and second stop members. The handle is pivotably connected to the transverse element and comprises a locking element for engaging a selected one of the recesses to enable fixation of a height of the structure relative to the caster wheel.
A method is provided for adjusting the height of a wheel, such as a caster wheel, relative to a structure such as the mower deck of a lawnmower. The caster wheel is supported by a frame that comprises an angled section. The angled section extends through a hollow guide member that is attached to the structure. The guide member and angled section are oriented along an adjustment direction that is angled relative to a ground surface on which the caster wheel is disposed. A lever is initially locked in engagement with a first recess of the angled section. The lever is grasped and pivoted out of engagement with the first recess into an unlocked position, while the lever is used to support a weight of at least a portion of the structure. In the unlocked position, the angled section is freely slidable through the guide member along the adjustment direction. A second recess of the angled section is selected. The second recess is spaced from the first recess at a distance generally along the adjustment direction. The angled section is slid through the guide member to an adjusted position that corresponds to a new height of the caster wheel relative to the structure. The angled section is slid along the adjustment direction by moving the lever along a vertical direction generally perpendicular to the ground surface, thereby raising or lowering the lever and consequently raising or lowering the structure. The angled section is locked at the adjusted position by releasing the lever. The angled orientation of the angled section and guide member, and the weight of at least the portion of the structure, cooperatively cause the lever when released to pivot into locked engagement with the selected second recess. In some embodiments, the pivoting of the lever into engagement with the selected second recess can be assisted through the use of a torsion spring that can be, for example, attached to the lever and wound around an axis about which the lever pivots.
It is therefore an object of the invention to provide a height adjustment apparatus and method for interconnection between one or more wheels, such as caster wheels, and a structure for which height adjustment is desired relative to the wheel or wheels and the ground, without impairing operation of the wheel or wheels.
An object of the invention having been stated hereinabove, and which is achieved in whole or in part by the invention disclosed herein, other objects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.